1. Field of the Invention
The present invention relates to a swash plate type refrigerant compressor non-exclusively adapted for use in compression of a refrigerant gas for an air-conditioning system of an automobile. More particularly, it relates to the internal construction of a swash plate type compressor having double-headed and swash plate-operated reciprocatory pistons and a rotary control valve for distributing refrigerant gas from a suction chamber to each of cylinder bores.
2. Description of the Related Art
U.S. Pat. No. 4,781,539 to Ikeda et al and assigned to the same Assignee as the present patent application discloses a typical swash plate type refrigerant compressor having double-headed reciprocatory pistons. The typical swash plate type refrigerant compressor having double-headed pistons is provided with a cylinder block in which a plurality of axial cylinder bores is formed to permit the double-headed pistons to reciprocate therein thereby effecting suction and compression of the refrigerant gas, and delivery of the compressed refrigerant gas. The cylinder block is also provided with a swash plate chamber formed therein so as to permit the swash plate mounted on a drive shaft to rotate together with the drive shaft.
Another typical swash plate type refrigerant compressor similar to the compressor of U.S. Pat. No. 4,781,539 is shown in FIGS. 4 and 5. Referring to FIGS. 4 and 5, the swash plate type refrigerant compressor includes a pair of front and rear cylinder blocks 33a and 33b axially combined together by using a plurality of screw bolts 35, and an axial drive shaft 34 rotatably supported by the cylinder blocks 33a and 33b via rotary bearings 41. The axially combined cylinder blocks 33a and 33b are provided with a plurality of pairs of axially aligned cylinder bores 42a and 42b in which double-headed pistons 36 are slidably received, and a swash plate chamber 48 for receiving a swash plate 37. The respective pairs of cylinder bores 42a and 42b are equi-angularly arranged around the axis of the drive shaft 34, as best illustrated in FIG. 5.
The drive shaft 34 has the above-mentioned swash plate 37 that is fixedly supported thereon so as to be capable of rotating together with the drive shaft. The swash plate 37 is axially supported by a pair of thrust bearings 40 arranged between inner shoulders of the front and rear cylinder blocks 33a, 33b and the swash plate 37 per se. Namely, any thrust force axially acting on the swash plate 37 and the drive shaft 34 during the compressing of the refrigerant gas is assumed by the thrust bearings 40, and thus the drive shaft 34 and the swash plate 37 are capable of rotating smoothly.
Each of the double-headed pistons 36 is provided with a recess 38 formed therein at a middle portion thereof and opening radially inwardly with respect to the axis of the drive shaft 34 so as to permit the swash plate 37 to pass through each piston 36 during rotating of the swash plate 37. In the recess 38 of each double-headed piston 36, a pair of semi-spherical shoes 39 operatively engaging the swash plate 37 with the double-headed piston 36 are arranged so as to smoothly generate a reciprocatory motion of the double-headed piston 36 from the rotational motion of the swash plate 37. Thus, during one complete rotation of the drive shaft 34 and the swash plate 37, each of the double-headed pistons 36 implements one complete stroke of reciprocation to thereby effect suction, compression and discharge of the refrigerant gas.
Front and rear housings 44 and 45 sealingly attached to the ends of the axially combined cylinder blocks 33a and 33b via front and rear valve plates 43a and 43b are provided with front and rear suction chambers 46a and 46b, and front and rear discharge chambers 47a and 47b formed therein, respectively. The suction chambers 46a and 46b of the front and rear housings 44 and 45 are communicated with the swash plate chamber 48 via passageways 51a and 51b formed in the front and rear cylinder blocks 33a and 33b. Thus, the refrigerant gas before compression returning from the external air-conditioning system is received by the swash plate chamber 48, and is further conveyed into the suction chambers 46a and 46b via the passageways 51a and 51b. The refrigerant gas entering the suction chamber 46a and 46b is further drawn into respective cylinder bores 42a and 42b via suction ports 49a and 49b formed in the front and rear valve plates 43a and 43b in response to the reciprocatory motion of the double-headed pistons 36.
The refrigerant gas in the respective cylinder bores 42a and 42b is compressed by the double-headed pistons 36, and the compressed refrigerant gas is discharged from the respective cylinder bores 42a and 42b toward the discharge chambers 47a and 47b of the front and rear housings 44 and 45 through discharge ports 50a and 50b formed in the front and rear valve plates 43a and 43b. The compressed refrigerant gas is then delivered from the discharge chambers 47a and 47b toward the air-conditioning system.
Nevertheless, when a consideration is given to the internal construction of the above-described conventional swash plate type refrigerant compressor, it is understood that an internal route of the refrigerant gas extending from the gas inlet of the compressor to each cylinder bore 42a or 42b is very long resulting in pressure loss of the refrigerant gas, and accordingly, the compression efficiency of the swash plate type refrigerant compressor is lowered while making it difficult to lessen the overall size of the compressor body.
Further, since each of the front and rear housings 44 and 45 is provided with both suction and discharge chambers 46a, 47a and 46b, 47b, it is difficult to obtain a sufficient spacing in both housings for arranging anti-friction and load supporting bearings for the drive shaft 34 without provision of any extension of the housings. Therefore, the anti-friction and thrust assuming bearings 40 and 41 must be arranged in the combined cylinder blocks 33a and 33b. However, the combined cylinder blocks per se are provided with only a limited amount of spacing for incorporating therein the anti-friction and thrust assuming bearings. Accordingly, two different kinds of bearings, i.e., a pair of anti-friction rotary bearings 41 and the other pair of thrust bearings 40 are individually arranged in the limited amount of spacing within the combined cylinder blocks 33a and 33b for supporting the drive shaft 34 and the swash plate 37. Consequently, neither the distance between the two thrust bearings 40, nor that between the two rotary bearings 41 can be long enough to stably support the drive shaft 34 and the swash plate 37 over a wide range of rotating speeds of the drive shaft 34 and the swash plate 37. As a result, the drive shaft 34 and the swash plate 37 is apt to vibrate when a large load applied to the compressor. This results in a reduction of the reliability of the swash plate type refrigerant compressor.